The present invention relates to a soluble isoflavone composition, a method for the preparation of the same and foods comprising the same.
It has been elucidated, by recent studies, that isoflavone included in beans such as soybean is a substance exhibiting various physiological activities such as an estrogenic activity, an antioxidant effect, an antibacterial activity, an antitumorigenic or anticarcinogenic activity and an effect of inhibiting bone density-reduction and thus, the usefulness thereof has been reappreciated from the viewpoint of prevention of, for instance, various cancers or tumors such as breast cancer and prostate cancer and osteoporosis and from the viewpoint of improving or promoting health.
The Japanese people has conventionally been in the habit of eating a large quantity of processed bean foodstuffs such as soybean curd, soybean milk, dried bean curd, fermented soybeans, cooked beans, miso and soy sauce and therefore, the Japanese people has conventionally ingested a large quantity of isoflavone without the intention of taking the same. However, the quantity of isoflavone taken by the Japanese people has gradually been reduced because of the westernization of the eating habits of the Japanese people. This accordingly results in the reduction of the amount or frequency of eating such processed bean foods, or an increase in the number of such processed foods whose isoflavone content has been reduced because of, for instance, the palate of the Japanese people. This would in turn be considered to be a cause of, for instance, increased number of patients suffering from osteoporosis, which is often observed for women at the turn of life.
Isoflavone has been commercialized in the form of powder prepared by extracting it from raw materials such as soybeans. However, these powdery products are hardly soluble in water, have strong bitterness, a rough taste and astringency as well as gritty feeling. For this reason, these powdery products are considerably limited in the application to foods or the like and accordingly, there has been a demand for the improvement thereof.
As a method for such improvement, there has been proposed a method, which comprises encapsulating isoflavone into cyclodextrin to thus solubilize the same in water. For instance, Japanese Un-Examined Patent Publication (hereunder referred to as xe2x80x9cJ.P. KOKAIxe2x80x9d) No. Hei 9-309902 discloses isoflavone derivatives prepared by encapsulating isoflavone derivatives contained in soybeans or fermented soybeans into at least one of xcex2-cyclodextrin and xcex3-cyclodextrin; and J.P. KOKAI No. Hei 10-298175 discloses a method for preparing easily water-soluble soybean isoflavone by bringing an extract obtained from raw soybeans into contact with cyclodextrin in an aqueous solution to thus remove impurities. Each beverage such as a fruit drink or juice comprise unique flavoring components, flavors are added to these beverages to distinguish one from another and/or fancy flavors are imparted thereto. If cyclodextrin is used, however, such flavoring components and fragrance-emitting components are also encapsulated into the same and this accordingly impairs the emission of the perfume peculiar to each particular drink. In addition, the isoflavone encapsulated into cyclodextrin suffers from problems in that it is not always sufficient in the solubility in water, even beverages, which must be transparent become turbid due to the addition of such encapsulated isoflavone and this accordingly results in the reduction of the commercial value of the beverages.
As has been described above in detail, the isoflavone, which is made soluble in water by the conventional method, suffers from such problems that it is still insufficient in solubility in water and that it is greatly limited in its application depending on the kinds of foods. For this reason, there has been a strong demand for the development of a soluble isoflavone composition free of such problems.
Accordingly, it is an object of the present invention to provide a soluble isoflavone composition, which has high solubility in water, is easily dissolved in water, stable over a long time period and can be incorporated into various kinds of foods without changing characteristic properties peculiar thereto.
It is another object of the present invention to provide a method for preparing the soluble isoflavone composition.
It is still another object of the present invention to provide a food comprising the foregoing soluble isoflavone composition.
The inventors of this invention have conducted various studies to solve the foregoing problems associated with the conventional techniques, have found that the foregoing objects can effectively be accomplished through the use of propylene glycol and/or octenyl succinate-treated starch as solubilizing agents and have thus completed the present invention on the basis of the foregoing finding.
According to an aspect of the present invention, there is provided a soluble isoflavone composition, which comprises isoflavone and anhydrous or water-containing propylene glycol and/or octenyl succinate-treated starch as a solubilizing agent.
When the solubilizing agent is anhydrous or water-containing propylene glycol, the weight ratio of isoflavone to propylene glycol preferably ranges from 1:100 to 10:100 and more preferably 1:100 to 7:100.
On the other hand, if octenyl succinate-treated starch is used as the solubilizing agent, the weight ratio of isoflavone to octenyl succinate-treated starch preferably ranges from 2:100 to 25:100 and more preferably 2:100 to 20:100.
Moreover, if the solubilizing agent used comprises a mixture of anhydrous or water-containing propylene glycol with octenyl succinate-treated starch, the weight ratio of isoflavone to propylene glycol preferably ranges from 1:100 to 10:100 and more preferably 1:100 to 7:100 and the weight ratio of isoflavone to octenyl succinate-treated starch preferably ranges from 2:100 to 25:100 and more preferably 2:100 to 20:100.
The soluble isoflavone composition of the present invention is preferably in the form of a stock solution or powder.
According to another aspect of the present invention, there is provided a food comprising the foregoing soluble isoflavone composition. Specific examples of such foods include fruit juices, juices, sport drinks, soups, jellies, coffee and black tea.
According to a further aspect of the present invention, there is provided a method for preparing a soluble isoflavone composition, which comprises the step of heating isoflavone and a solubilizing agent comprising anhydrous or water-containing propylene glycol and/or octenyl succinate-treated starch in the presence of water to thus solubilize isoflavone in water.
The heating temperature is not restricted to any specific range inasmuch as it is sufficient to dissolve isoflavone in water, but preferably ranges from 70 to 100xc2x0 C., more preferably 80 to 95xc2x0 C. and most preferably 85 to 95xc2x0 C.
According to a still further aspect of the present invention, there is also provided a method for preparing a soluble isoflavone composition in the form of powder, which comprises the steps of heating isoflavone and a solubilizing agent consisting of octenyl succinate-treated starch in the presence of water to thus solubilize isoflavone in water and then drying the solution.
The term xe2x80x9cisoflavonexe2x80x9d is a general term for isoflavone derivatives such as daidzein, glycitin and genistein present in beans such as soybeans. It is quite difficult to isolate these isoflavone derivatives, in their pure conditions, from soybeans or the like and in many cases, they are put on the market in the form of mixtures containing, for instance, soybean saponin and/or soybean proteins. In the present invention, the term xe2x80x9cisoflavonexe2x80x9d is used to embrace mixtures containing, for instance, soybean saponin and/or soybean proteins, preferably those containing not less than 30% by weight of isoflavone, in addition to pure isoflavone.
Such isoflavone is prepared by, for instance, a method disclosed in J.P. KOKAI No. Hei 4-266898, which comprises pulverizing embryo axes of soybeans, extracting from the pulverized embryo axes three times with 70% water-containing alcohol, again extracting with a butanol-water mixed solvent and then drying; a method disclosed in J.P. KOKAIMNo. Hei 10-23878, which comprises the steps of heating an aqueous soybean molasses solution prepared by removing the ethanol from an ethanol to water extract of defatted soybean flakes, subjecting the aqueous solution to ultrafiltration to give a filtrate and separating isoflavone from the filtrate by cooling the same to thus recover the isoflavone; a method which comprises adsorbing isoflavone present in such an extract on an adsorbing resin and then eluting the isoflavone from the resin with an alcohol-water mixed solvent; or a method disclosed in J.P. KOKAI No. Hei 10-316671, which comprises removing the alcohol from an alcohol extract of soybeans or the like, solubilizing the isoflavone compounds through the addition of an alkali and then acidifying the solution to thus separate and recover the isoflavone compounds.
In the present invention, the term xe2x80x9csolubilized isoflavonexe2x80x9d means isoflavone obtained by treating untreated isoflavone hardly soluble in water with a solubilizing agent or isoflavone whose solubility in water is improved through such a treatment.
The present invention is characterized in that the solubilizing agent used for solubilizing isoflavone comprises anhydrous or water-containing propylene glycol and/or octenyl succinate-treated starch.
If isoflavone is heated in anhydrous or water-containing propylene glycol at a temperature ranging from 70 to 100xc2x0 C., preferably 80 to 95xc2x0 C. and more preferably 85 to 95xc2x0 C., isoflavone is completely dissolved therein to give a transparent solution. This is because if the heating temperature is less than 70xc2x0 C., isoflavone is not sufficiently dissolved in the anhydrous or water-containing propylene glycol and it is thus difficult to obtain a transparent solution, while even if the temperature exceeds 100xc2x0 C., the transparency of the resulting solution is not improved any more.
The weight ratio of isoflavone to propylene glycol preferably ranges from 1:100 to 10:100 and more preferably 1:100 to 7:100.
The concentration of propylene glycol in the water-containing propylene glycol is not restricted to any particular range inasmuch as the amount of isoflavone dissolved therein is greater than the amount thereof capable of being solubilized in water, when heating isoflavone in the water-containing propylene glycol. When isoflavone is dissolved in the water-containing propylene glycol with heating, however, the solubility of isoflavone in the solubilizing agent abruptly increases at a propylene glycol concentration of about 20% by weight or higher, the solubility thereof reaches the maximum level at a propylene glycol concentration of about 80% by weight and isoflavone is soluble even in propylene glycol per se. For this reason, the propylene glycol concentration in the solubilizing agent preferably ranges from 20 to 100% by weight, more preferably 50 to 100% by weight and most preferably 60 to 100% by weight.
The solubilized isoflavone, i.e., the soluble isoflavone composition according to the present invention can easily provide an aqueous solution simply by addition thereof to water and the aqueous solution maintains its transparency when the temperature thereof is held at a level of not less than about 60xc2x0 C. Moreover, the soluble isoflavone composition of the present invention can be stored over a long period of time and therefore, a desired amount thereof can be used at need. On the other hand, when storing the solution at room temperature or a low temperature in a refrigerator, the solution sometimes becomes turbid or forms precipitates of isoflavone, but the precipitates are very small in size and they can easily be dispersed, as compared with a dispersion obtained by simply suspending isoflavone in water.
Isoflavone may be dissolved in anhydrous or water-containing propylene glycol each time, but it is quite convenient that isoflavone is previously dissolved in anhydrous or water-containing propylene glycol to give a stock solution thereof and to store the same. The stock solution is in general stored at room temperature. In such case, the anhydrous or water-containing propylene glycol preferably has a propylene glycol concentration ranging from 60 to 100% by weight since the resulting isoflavone solution is stable even if it is stored over a long period of time.
The isoflavone solution thus obtained can maintain its transparency when it is heated, in particular, to a temperature of not less than 60xc2x0 C. Therefore, if the composition of the present invention is added to a hot drink such as coffee, black tea or soup, the drink is not cloudy or does not cause any precipitation at all. In addition, the solution may form precipitates to some extent when storing it in a refrigerator, but the resulting precipitates are very small in size and can easily be dispersed in the solution. Therefore, when it is added to drinks such as fruit drinks, which are cloudy, by nature, any significant problem does not arise.
The octenyl succinate-treated starch used in the present invention, as a solubilizing agent is a product obtained by acting an esterifying agent such as anhydrous octenyl succinate on starch and includes octenyl succinate-treated starch whose molecular weight is reduced, as well.
The octenyl succinate-treated starch may be either hot water-soluble or cold water-soluble one. If isoflavone is used for general purposes, the size of the octenyl succinate-treated starch is not a serious problem, but when isoflavone is used in, for instance, drinks requiring high transparency, more preferably used is low molecular weight octenyl succinate-treated starch or one having a viscosity, as determined using a 20% by weight aqueous solution, ranging from 10 to 100 cp. If the viscosity of the aqueous solution is less than 10 cp, a greater amount of the solution is required for achieving the same effect, while if it exceeds 100 cp, the transparency of the resulting solution is slightly impaired. In this connection, the viscosity, as determined using a 20% by weight aqueous solution, is measured using a Brookfield rotational viscometer at a temperature of 30xc2x0 C. The aqueous solution is prepared by dispensing 40 g of a sample and 160 g of water into a beaker having an inner volume of 200 ml to give an aqueous solution, in case of cold water soluble samples, or further heating the resulting-mixture up to 90xc2x0 C., then cooling the resulting solution and compensating the loss of water due to evaporation, in case of hot water-soluble samples.
The molecular weight of the octenyl succinate-treated starch can be reduced by, for instance, a method for preparing soluble starch, which comprises acting an acid such as sulfuric acid or hydrochloric acid or an oxidizing agent such as sodium hypochlorite on starch in particulate states to thus decompose the starch; or a method for preparing maltodextrin, which comprises adding an acid such as oxalic acid or hydrochloric acid or amylase to starch and then heating the mixture to convert the starch into a glue and to thus decompose the same. Low molecular weight starch such as those soluble starch type ones are soluble in hot water, while those of maltodextrin type ones are soluble in cold water. In addition, the soluble starch type ones may be subjected to esterification after the decomposition. In this respect, the soluble starch type ones, which are soluble in hot water, may be converted into cold water-soluble ones by treating them with a drum dryer or an extruder.
Raw starch materials to be used are not restricted to any particular one and a variety of starches may be used. Specific examples thereof include naturally occurring starches such as potato starch, tapioca starch, wheat starch, cornstarch, waxy cornstarch, sago starch and glutinous rice starch; and processed starches such as those prepared by treating naturally occurring starches through various means such as bleaching and conversion into hydroxypropyl derivatives thereof.
If octenyl succinate-treated starch is used as the solubilizing agent, the weight ratio of isoflavone to octenyl succinate-treated starch preferably ranges from 2:100 to 25:100 and more preferably 2:100 to 20:100.
In this case, isoflavone can be solubilized by heating it in water containing octenyl succinate-treated starch in an amount of 4 to 50 times that of the isoflavone at a temperature preferably ranging from 70 to 100xc2x0 C. and more preferably about 80 to 95xc2x0 C. to thus give an aqueous-solution of isoflavone. The concentration of isoflavone in the aqueous solution is suitably limited to not more than about 1% by weight.
If the amount of an octenyl succinate-treated starch is less than 4 times that of isoflavone, it is sometimes difficult to obtain any transparent aqueous solution of isoflavone, while the use of an octenyl succinate-treated starch in an amount of more than 50 times that of isoflavone does not show any further effect of improving the stability of the resulting isoflavone aqueous solution. On the other hand, if the heating temperature is less than 80xc2x0 C., in particular, less than 70xc2x0 C., isoflavone is insufficiently dissolved in water and accordingly, a transparent solution cannot always be prepared, while the use of the heating temperature higher than 95xc2x0 C. does not ensure any further effect of improving the transparency of the resulting aqueous solution.
The octenyl succinate-treated starch may be either hot water-soluble type ones or cold water-soluble type ones. Isoflavone and octenyl succinate-treated starch are added to water without any pre-treatment or these components in their powdery states are admixed together in advance and then dispersed in water prior to heat the dispersion. Alternatively, octenyl succinate-treated starch is first dissolved in water, then isoflavone is introduced into the resulting aqueous solution and thereafter the mixture is heated. In any case, it is important to heat isoflavone in the presence of octenyl succinate-treated starch.
The solubilized isoflavone aqueous solution thus prepared can effectively maintain its transparency over a long period of time irrespective of the manner of storage, for instance, storage at a high temperature, room temperature or a low temperature. Therefore, the aqueous solution is suitable for use in foods requiring high transparency such as consomme soup.
The isoflavone composition, which is made water-soluble by the use of an octenyl succinate-treated starch, can freely be diluted with water. Therefore, in the present invention, isoflavone can be used or stored in the form of a stock solution having a concentration higher than a desired one. In such case, the concentration of isoflavone, which can be solubilized in water, is relatively low on the order of up to about 0.2% by weight at a low temperature and up to about 1% by weight at a high temperature.
For this reason, the soluble isoflavone composition is more preferably used or stored in a powdery condition. The isoflavone composition may be powdered by, for instance, a method comprising the step of drying an isoflavone aqueous solution having the highest possible concentration and prepared by the foregoing method. Drying methods usable herein may be any conventionally known drying methods such as lyophilization (or freeze-drying), spray drying and drying in a drum dryer. At this stage, it is also possible, as a means for improving the drying efficiency, to add, to the isoflavone solution, at least one member suitably used as ingredients of each desired food and selected from the group consisting of sugar, glucose, maltose, lactose, starch hydrolyzates decomposed to a DE value ranging from about 3 to 25 and hydrolyzates of reduced starch thereof, to thus increase the concentration of the aqueous solution prior to the drying step.
The powdered soluble isoflavone composition thus prepared is easily dissolved in both cold and hot water. The powdery composition can be stored over a long period of time and thus can be used in a desired amount at need. It is also possible to incorporate into fast foods such as soup, which can be regenerated simply by addition of hot water.
When solubilizing isoflavone using an octenyl succinate-treated starch as a solubilizing agent, it is necessary to heat these components, in the coexistence thereof and a problem arises, such that the concentration of isoflavone is rather too low to prepare a stock solution.
As a method for eliminating the foregoing problem, there may be listed, for instance, a method which comprises solubilizing isoflavone using both octenyl succinate-treated starch and propylene glycol. More specifically, the foregoing isoflavone is dissolved in anhydrous or water-containing propylene glycol to prepare an isoflavone solution having a relatively high concentration as a stock solution, and then adding the stock solution to an aqueous solution of octenyl succinate-treated starch to thus give an aqueous isoflavone solution, which has a relatively high isoflavone content and stability over a long period of time even when stored at a low temperature. The preliminary preparation of an aqueous solution of octenyl succinate-treated starch is quite convenient, since it can be added to the stock solution at any stage during the preparation of a food and at an arbitrary temperature. In this case, the ratio of the octenyl succinate-treated starch to isoflavone is preferably approximately identical to that used for solubilizing isoflavone using the succinate-treated starch because of the stability of the resulting solution.
When simultaneously using these anhydrous or water-containing propylene glycol and octenyl succinate-treated starch, a stock solution having a high isoflavone concentration can be prepared due to the use of propylene glycol and the resulting solution can be stored over a long period of time, while the use of the octenyl succinate-treated starch permits the saving of the time required for dissolving isoflavone each time and the maintenance of the stability of the aqueous solution even when it is kept in the cold storage and/or stored under acidic conditions. Therefore, the solution can be added to a wide variety of foods.
The isoflavone solution prepared using octenyl succinate-treated starch or the combination of octenyl succinate-treated starch and anhydrous or water-containing propylene glycol is excellent in transparency, never undergoes any change even when it is kept in cold storage over a long period of time and is suitable for use in a variety of foods, in particular, those requiring high transparency such as beverages or drinks and soups.
Incidentally, the amount of isoflavone required for the adult per day is believed to be about 40 mg as expressed in terms of the amount of the effective component. Isoflavone can be taken to a certain degree as the ordinary diet, but the correct amount thereof would considerably vary depending on the difference in race and eating habits. In addition, the intake of isoflavone has recently been reduced and has been lower than the foregoing required amount even in the Asian races, who are in habit of taking a wide variety of soybean foods, because of the wide spread of processed bean foods. The soluble isoflavone composition of the present invention can be added to foods such as drinks or soup to thus easily supplement a proper amount of isoflavone, whose intake is insufficient.
Accordingly, the foods containing the soluble isoflavone composition of the present invention preferably contain isoflavone in an amount ranging from about 5 to 40 mg per food usually taken per day.
Moreover, the water used for preparing the soluble isoflavone composition of the present invention may contain other components, for instance, sweeteners such as sugar, isomerized sugar, fruit sugar and synthetic sweeteners; a variety of fruit juices; acidulants; and flavors.